I just have some unrelated thoughts. I think that after a certain level but without getting anywhere near the ceiling, it does become harder to make significant gains on the reading MAP. Part of it is due to the lack of exposure to certain technical literary terms and techniques, rather than actual reading comprehension level or fluency. On that basis, I wouldn't worry about the stagnant reading scores so much if you are seeing real life gains.
Excellent advice.
While the MAP 2-5 does purportedly test to the same high levels as the MAP 6+, in reality it might at times be harder to get those super high scores due to more limited test items. There is the additional argument that even if you get the super high scores on the MAP 2-5, it may not be as accurate. Again, I don't really have an opinion and personally don't worry about it too much. However, I do have written evidence that it is possible to get a score of at least 280 on MAP 2-5 Math and a score of at least 250 on the MAP 2-5 Reading. I believe that the scale on the MAP 6+ goes up to 300 so theoretically it should also go up to 300 on the MAP 2-5 as well.
To your last point: Not necessarily, as they are continuously-scaled across grade levels. There may not be, as you rightly point out, enough items (if any) of difficulty level 300 on the 2-5 reading test to obtain a 300 score. Also, as these are Rasch scores, and not deviation scores, comparing scores in one subject area to another is even more sketchy than usual. (NWEA specifically says not to do it.)
